Abstract According to the approach inhibition theory of power, powerful lead to behavior approach tendency, powerless lead to behavior inhibition tendency under the condition of stable power relationship. However, when the power is no longer stable, it is unknown that the relationship between powerful and behavior approach tendency, and the relation between powerless and behavior inhibit tendency are still the same, or will be broken and even reversed. Therefore, the current study assumed that under unstable power condition, powerful exhibited more behavior inhibition tendency, powerless showed more behavior approach tendency. In addition, current study also hypothesized that power motivation enhanced this reverse effect, to be specific, the higher power motivation was, the more obvious behavior inhibition tendency of powerful was, and the more obvious behavior approach tendency of powerless was. Two experiments were designed to test these ideas. In Experiment 1, role play method was adopted to manipulate sense of power and instability of power. All participants were randomly assigned to play role of "distributor" (high power) or the role of "recipient" (low power) in gambling task. Under the condition of power instability, participants were told that their role will be adjusted according to their performance in gambling task, while participants under the condition of power stability were not informed with this. Then participants accomplished gambling task for measuring power effect in which they decided to choose different strategy of wining rewards, one was conservative decision strategy to make small gain and loss, the other was risk decision strategy to make big gain or loss. Experiment 2 adopted the real role assignment method to manipulate sense of power and instability of power. All participants were randomly appointed with “distributors”(high power) or “recipients” (low power) in money allocation tasks. After role assignment, participants were asked to complete two round of money allocation task of taking the benefit-oriented behaviors in money allocation to measure the effect of power. The role of “distributors” or “recipients” can not be changed during the first round (power stability condition), while during the second round of money allocation task (power instability condition), all participants were informed if the “distributor” did not perform well, his role will be degraded into “recipient”, meanwhile the previously related “recipient” will be turned to be “distributor” in the third round. The result of experiment showed that, under the condition of stable power, the powerful showed more risk behaviors and more benefit oriented behaviors over the powerless; while in the condition of unstable power, the powerless showed more risk behaviors and more benefit oriented behavior over the powerful. In addition, the individual power motivation not solely enhance the inhibition tendency of the powerful’s benefit oriented behaviors, but also promote the approach tendency of the powerless’s benefit oriented behaviors. This research confirmed that instability of power possesses reverse impact upon power effect and the power motivation functions as enhancement to the reverse effect.